Preparation of 1,1,2,3-tetrachloropropene from 1,2,3-trichloropropane

ABSTRACT

THIS PROCESS PREPARED 1,1,2,3-TETRACHLOROPROPENE FROM 1,2,3-TRICHLOROPROPANE. 1,2,2,3-TETRACHLOROPROPANE IS OBTAINED AS A BY-PRODUCT. THE PRODUCT AND BY-PRODUCT OF THIS PROCESS ARE USEFUL AS INTERN.EDIATES IN THE PREPARATION OF PESTICIDES.

United States Patent C 3,823,195 PREPARATION OF 1,1,2,3-TETRACHLOROPRO-PENE FROM 1,2,3-TRICHLOROPROPANE Lowell R. Smith, Chesterfield, Mo.,assiguor to Monsanto Company, St. Louis, M0. N Drawing. Filed Dec. 27,1971, Ser. No. 212,742 Int. Cl. C07c 21/04 US. Cl. 260-654 R 8 ClaimsABSTRACT OF THE DISCILOSURE This process prepared1,1,2,3-tetrachloropropene from 1,2,3-trichloropropane.1,2,2,3-Tetrachloropropane is obtained as a by-product. The product andby-product of this process are useful as intermediates in thepreparation of pesticides.

This invention relates to the preparation of chlorinated hydrocarbons.More particularly it relates to the preparation of1,1,2,3-tetrachloropropene from 1,2,3-trichloropropane.1,2,2,3-Tetrachloropropane may also be recovered from the process as aby-product.

1,1,2,3-Tetrachlor0propene and 1,2,2,3-tetrachloropropane are importantintermediates in the preparation of pesticides, more particularlyselective herbicides for the control of noxious weeds in various crops.S(2,3,3-trichloroallyl)diisopropylthiolcarbamate, described in US. Pat.No. 3,330,821, is an example of a selective herbicide which can beprepared from 1,1,2,3-tetrachloropropene. S-(2,3dichloroallyl)diisopropylthiolcarbamate, also described in U.S. Pat. No.3,330,821, may be prepared using an intermediate prepared from1,2,2,3-tetrachloropropane as described in copending application, Ser.No. 210,268, filed Dec. 17, 1971, by Lowell R. Smith, entitled Processfor Preparing 1,2,3-Trichloropropene. Because of the growing demand foreffective herbicides and pesticides in general, there is an industryneed for more eificient processes for the preparation of pesticides. Thepresent process provides a new method for preparing1,1,2,3-tetrachloropropene in higher yields and with lower levels ofchlorinated waste products than any of the methods of the prior art.

The present invention is a process which comprises (A) feeding a streamcomprising 1,2,3-trichloropropane to a liquid-phase chlorinator,

(B) chlorinating the feed stream so that from about to about 60 percentby weight of the chlorinator effluent remains as unreacted1,2,3-trichloropropane,

(C) passing the chlorinator etfiuent which comprises1,2,3-trichloropropane, 1,1,2,3-tetrachloropropane,1,2,2,3-tetrachloropropane, 1,1,1,2,3-pentachloropropane,1,1,2,2,3-pentachloropropane, and 1,1,2,3,3-pentachloropropane to afractionating column, (D) fractionating said chlorinator efiluent into a1,2,3-trichloropropane fraction, a 1,2,2,3-tetrachloropropane fraction,a 1,1,2,3-tetrachloropropane fraction, a 1,1,1,2,3- and1,1,2,2,3-pentachloropropanes fraction and a1,1,2,3,3-pentachloropropane and heavy ends fraction,

(1) recycling the 1,2,3-trichloropropane fraction to the chlorinator,(2) removing the 1,2,2,3-tetrachloropropane fraction, v(

(a) passing the 1,1,2,3-tetrachloropropane fracice tion from thefractionating column to a caustic dehydrochlorinator,

(b) dehydrochlorinating the 1,1,2,3-tetrach1oropropane,

(c) passing the dehydrochlorinator efliuent which comprises1,1,2-trichloropropene, 1,2,3- trichloropropene, and2,3,3-trichloropropene, to a second liquid-phase chlorinator,

((1) adding chlorine to the carbon/ carbon double bond of the compoundscontained in the dehydrochlorinator efiiuent,

(e) passing the second chlorinator efiiuent Which comprises 1,1,1,2,3-pentachloroprop ane, and 1,1,2,2,3 pentachloropropane, to a secondcaustic dehydrochlorinator,

(4) passing the 1,1,1,2,3- and 1,1,2,2,3-pentachloropropanes fractionfrom the fractionating column to the second caustic dehydrochlorinator,

(F) dehydrochlorinating the second chlorinator etfiuent and thel,1,1,2,3- and 1,1,2,2,3-pentachloropropanes fraction from thefractionating column,

(G) passing the second dehydrochlorinator efiluent, which comprisesl,1,2,3-tetrachloropropene, and 2,3,3,3-tetrachloropropene, to anisomerizer packed with siliceous granules having a polar surface, and

(H) isomerizing the 2,3,3,3-tetrachloropropene to 1,1,2,3-

tetrachloropropene by heating the second dehydrochlorinator efiluent incontact with the siliceous granules to a temperature of from about C. toabout 200 C. for from about 0.4 to about 2 hours.

The liquid-phase chlorinator substitutes chlorine for hydrogen by thefree radical method. Formation of freeradicals may be initiated byexposing the contents of the chlorinator to actinic light or byconducting the chlorination in contact with a catalytic amount of afree-radical forming catalyst such as one of the peroxides, i.e. benzoylperoxide, lauryl peroxide, cumene peroxide, urea peroxide tertiary butylperoxide, etc., or other free-radical formers such asazobisisobutyronitrile, etc. These liquid-phase chlorination methods areWell known to the skilled artisan and the particular method employed isnot a part of the invention. However, it is critical that the extent ofchlorination of the feed stream be controlled so that from about 20 toabout 60 percent by weight of the feed remains as unreacted1,2,3-trichloropropane in order to limit the number of chlorinatedproducts obtained. It is preferred to chlorinate so that from about 30to about 50 percent by weight of the feed stream remains unreacted, andmore preferred to chlorinate so that from about 35 to about 45 percentby weight of the feed stream remains unreacted.

Control of the chlorination within the stated limits gives an effluentcomprised of the following compounds with boiling points as shown:

Boiling point degrees, Centigrade C.)

1,2,3-trichloropropane 157 1,2,2,3-tetrachloropropane 1631,1,2,3-tetrachloropropane 179 1,1,1,2,3-pentachloropropane 1911,1,2,2,3-pentachloropropane 191 1,1,2,3,3-pentachloropropane 198 Thecompounds are readily separated into 5 fractions in a conventionalfractionating column. The fractionating column may be of any suitabledesign and may utilize trays or packing to make the necessaryseparations. Since corrosion is a consideration, a packed column ispreferred. While the type of fractioning column is not critical, it isnecessary that the five fractions, comprised of the followingcomponents, be separated in order to obtain the high yields of thepresent process:

Fraction 11,2,3-trichloropropane Fraction 2-1,2,2,3-tetrachloropropaneFraction 3-1,1,2,3-tetrachloropropane Fraction 4l,1,1,2,3- and1,1,2,2,3-pentachloropropanes Fraction 5-1,l,2,3,3-pentachloropropaneFraction 1 generally consists essentially of 1,2,3-trichloropropane andany other light ends which may be present in the process. This entirestream is recycled to the chlorinator.

Fraction 2 is a by-product stream. The l,2,2,3-tetrachloropropane may beutilized, as is or after further purification, as a raw material inother processes. :It is preferred to use Fraction 2, as is, as a rawmaterial in the manufacture of 1,2,3-trichloropropene.

Fraction 3 is taken, as is, to a caustic dehydrochlorinator whichconverts the tetrachloropropane to a mixture of trichloropropenes. Thedesign of the dehydrochlorinator and the method of dehydrochlorinationin the presence of caustic are conventional and not critical to theinvention. After dehydrochlorniation the effluent which normallyconsists essentially of 1,1,3-trichloropropene, 1,2,3-trichloropropeneand 2,3,3-trichloropropene is passed to a second liquid-phasechlorinator. This second liquid-phase chlorinator by conventional meansadds chlorine at the double bond to form 1,1,2,2,3-pentachloropropaneand 1,1,1,2,3-pentachloropropane. The efiluent of this secondchlorinator is then passed to a second caustic dehydrochlorinator. Thehandling of Fraction 3 is another key feature of the process. Althoughthe methods employed are admittedly conventional, the result is novel.Fraction 3 as it passes from the fractionator is a useless by-product.However, by removing HCl and then adding C1 this useless by-product isconverted to a valuable precursor for 1,1,2,3-tetrachloropropene. Thisconversion is important in obtaining the high yield of product from thepresent process.

Fraction 4 is also passed to the second caustic dehydrochlorinator.Fraction 4 and the second chlorinator efiluent may enter the secondcaustic dehydrochlorinator as separate streams or as a single combinedstream. The method of operation of this second dehydrochlorinator is notcritical to the invention and may be the same as or different from themethod of operation of the dehydrochlorinator which dehydrochlorinatesFraction 3 to mixed trichloropropenes.

Fraction 5 is a waste stream. It may be sent directly to waste disposalor utilized for other purposes. The disposal or utilization of Fraction5 is not critical to the present invention.

The etfiuent from the second caustic dehydrochlorinator normallyconsists essentially of product 1,1,2,3- tetrachloropropene and2,3,3,3-tetrachloropropene. This stream is passed to an isomerizer whichconverts almost totally the 2,3,3,3-tetrachloropropene to1,1,2,3-tetrachloropropene. This isomerization is a particularly uniquefeature of the present process. The isomerizer is a vessel of anysuitable design packed with siliceous granules having a polar surface.The size and shape of the granules will vary depending on the particularoperating conditions desired for the isomerizer. Factors to beconsidered in determining granule size and shape are basically processdesign considerations known to the skilled process engineer, such aspressure drop across the vessel, vessel inventory, process flow rate,tolerable packing loss, etc. Siliceous, i.e. silica containing,compounds which may be used in this process include a variety ofcalcined and uncalcined clays such as montmorillonite, kaolinite,bentonite, hectorite, beidellite and attapulgite; other mineral salts ofsilica such as chrysolite, saponite, feldspar, quartz, wollastonite,mullite, kyanite, amosite, cristobalite, chrysotile, crocidolite, mica,spodumene and garnet; siliceous non-mineral substances such as silicagel, fumed silica, fibrous aluminum silicate and glass. It is preferredthat the granules be clay and more preferred that the granules beattapulgite.

The isomerizer operates at a temperature of from about C. to about 200C., preferably from about C. to about C. The isomerization is usuallycarried out at atmospheric pressure, but higher or lower pressures maybe utilized if equipment and other factors favor such higher or lowerpressures. The isomerization may be carried out in a closed vessel orunder reflux. It is particularly preferred to carry out theisomerization under reflux at atmospheric pressure. Under the statedconditions the second caustic dehydrochlorinator eflluent is isomerizedto a stream consisting essentially of 1,l,2,3- tetrachloropropene infrom about 0.4 to about 2 hours, preferably from about 0.5 to about 1.3hours and more preferably from about 0.6 to about 1 hour. The efiiuentfrom the isomerizer may be used, as is, in the preparation of S-(2,3,3trichloroallyl)diisopropylthiolcarbamate or further purified for use insaid preparation or other processes.

By this process about 39 percent by weight of 1,2,3-trichloropropane isconverted to 1,2,2,3-tetrachloropropane and about 46 percent by weightof 1,2,3-trichloropropane is converted to 1,1,2,3-trichloropropenegiving a total conversion to useful products of about 85 percent byweight of 1,2,3-trichloropropane.

As used herein, the term efiiuent refers to the product stream flowingfrom the specified vessel.

The following examples are presented as illustrative of the process ofthis invention and are not to be construed as limitative thereof.

EXAMPLE 1 This example illustrates an embodiment of the chlorinationstep in the process of this invention.

Chlorination of 1,003 grams (g) of 1,2,3-trichloropropane is carried outin an open vessel exposed to ultraviolet light from a 5 inch quartzshort wave lamp (2537 Angstrom units) suspended immediately above thesurface of the 1,2,3-trichloropropane. The vessel is heated to fromabout 40 to about 50% C. and about 355 grams of chlorine gas is bubbledthrough the 1,2,3-trichloropropane at a rate of from about 0.5 to about1 g. per minute. Upon completion of the chlorine addition thecomposition of the mass is determined by chromatographic analysis andfound to be about as follows:

Grams Percent 1,2,3-trichloropropane 483 40. 4 1,2,2,3tetraehloropropane 259 21. 7 1,1,2,3-tetrachloropropane 374 31. 31,1,1,2,3- and 1,1,2,2,3-pentachloropropan 88 3. 21,1,2,3,3-pentachloropropane and heavy ends 18 1. 5

Total 1, 172 98. 1

EXAMPLE 2 This example illustrates an embodiment of the chlorinationstep in the process of this invention.

The procedure of Example 1, except as noted below is followed to give achlorinator efiluent composition about as shown:

EXAMPLES 3 AND 4 These examples illustrate, chlorination outside theprocess of this invention.

* The procedure of Example 1'," except as noted below, is followed togive chlorinator-diluent compositions as shown:

' Example3 Example;

Total 9 EXAMPLE 5 This example illustrates the dehydrochlorination of1,1,2,3-tetrachloropropane.

The chlorinator eflluent of Example 1 is fractionated at a pressure offrom about 25 to about 36 millimeters of mercury in a 2 inch 20 trayOldershaw column. A 304.8 g. fraction comprising1,1,2,3-tetrachloropropane is removed and charged to a suitable vesselequipped with an agitator and heated to about 95 C. About 69.7 g. ofsodium hydroxide is dissolved in about 278.8 g. of water. This causticsolution is slowly added to said fraction over about 2% hours. The massis stirred for 2 /2 hours at about 95 C. It is determined that about 2.7percent of the feed remains unreacted and that the pH of the mass isabout 6.0. Thereupon about 2 g. of sodium hydroxide dissolved in about 2g. of water and a small quantity of an anti-foam agent is added. Themass is then heated at about 95 C. for an additional minutes. The massis then steam distilled until the vapor temperature is 99 C. Thedistillate forms two layers. The layers are separated and the organiclayer is found to weigh about 233.6 g. and to contain:

Percent by weight 1,1,3-trichloropropene 22 1,2,3-trichloropropene 672,3,3-trichloropropene 9 The mixed trichloropropenes are dried overmolecular sieves and filtered. About 228.5 g. are recovered.

EXAMPLE 6 This example illustrates the addition of chlorine to thecarbon/carbon double bond of mixed trichloropropenes.

The 228.5 g. of mixed trichloropropenes of Example 5 are charged to a.suitable open vessel and heated to about 55 C. The contents are exposedto ultra-violet light from a 5 inch quartz short wave lamp (2537Angstrom units) suspended immediately above the surface. About 111 g. ofchlorine gas are bubbled through the contents at a rate of about 0.5 to1 g. per minute. About 339.1 g. of 1,1,1,2,3- and1,1,2,2,3-pentachloropropanes are obtained. This chlorination as well asthe chlorination of Example 1 may be carried out with equal facility inthe presence of a catalytic amount of azobisisobutyronitrile or otherfree-radicalforming catalyst. When using such a catalyst the presence ofultra-violet light is not necessary.

EXAMPLE 7 This example illustrates the dehydrochlorination of mixedl,l,1,2,3- and 1,1,2,2,3-pentachloropropanes.

The 339.1 g. of 1,l,1,2,3- and 1,1,2,2,3-pentachloro-.

propanes obtained in Example 6 are charged to a suitable vessel equippedwith an agitator and heated to about C. About 65.2 g. of sodiumhydroxide are added to and dissolved in about 260.8 g. of water. Thissolution is slowly added to the mixed pentachloropropanes over a periodof about 1% hours. The mass is stirred at a temperature of about 95 C.for about 2 /2 hours and then steam distilled until the vaportemperature is 99 C. The distillate forms two layers. The layers areseparated and the organic layer is found to weigh about 263.5 goand tocontain:

Percent by weight 33.4

EXAMPLE 8 This example illustrates the isomerization of 2,3,3,3tetrachloropropene to l,l,2,3-tetrachloropropene.

The 263.5 grams of mixed tetrachloropropenes of EX- ample are charged toa suitable vessel equipped with a reflux condenser. To the mixedtetrachloropropenes is added about 30 grams of about 20 to 40 mesh (UJS.Sieve) granules of attapulgus clay. (Prior to this addition the clay ispreviously refluxed with mixed tetrachloropropenes then filtered but notdried in order to simulate continuous plant operation and minimize yieldloss by adsorption on the clays surface.) The mass is refluxed atatmospheric pressure for about 40 minutes and the clay is removed byfiltration. Analysis shows about 92.3 percent by weight yield of1,1,2,3-tetrachloropropene.

While this invention has been described with respect to certainembodiments, it is to be understood that it is not so limited and thatvariations and modifications thereof obvious to those skilled in the artto which this invention appertains can be made without departing fromthe spirit or scope thereof.

What is claimed is:

l. A process which comprises feeding a stream consisting essentially of1,2,3-trichloropropane to a liquidphase chlorinator, chlorinating thefeed stream with chlorine gas so that from about 20 to about 60 percentby weight of the chlorinator eifiuent remains as unreacted1,2,3-trichloropropane, passing the chlorinator eflluent to afractionating column, fractionating said chlorinator effiuent into a1,2,3-trichloropropane fraction, a 1,2,2,3- tetrachloropropane fraction,a l,1,2,3-tetrachloropropane fraction, a 1,l,1,2,3- and 1,1,2,2,3pentachloropropanes fraction, and a 1,1,2,3,3-pentachloropropane andheavy ends fraction, recyclingthe 1,2,3-trichloropropane fraction fromthe fractionating column to the chlorinator, passing the1,1,2,3-tetrachloropropane fraction from the 2,3,3,3-tetrachloropropene1,1,2,3-tetrachloropropene fractionating column to a causticdehydrochlorinator, de-

hydrochlorinating the 1,1,2,3-tetrachloropropane, passing thedehydrochlorinator effluent which comprises mixed trichloropropenes to asecond liquid-phase chlorinator, adding chlorine to the carbon/carbondouble bond of the trichloropropenes contained in the dehydrochlorinatoreffluent, passing the second chlorinator effluent which comprises1,1,1,2,3-pentachloropropane and 1,1,2,2,3- pentachloropropane to asecond caustic dehydrochlorinator, passing the 1,l,1,2,3- and1,1,2,2,3-pentachloropropanes fraction from the fractionating column tothe second caustic dehydrochlorinator, dehydrochlorinating the secondchlorinator efliuent and the 1,1,1,2,3- andl,1,2,2,3-pentachloropropanes fraction from the frac- -tionating column,passing the second dehydrochlorinator effiuent which comprisesl,1,2,3-tetrachloropropene and 2,3,3,3-tetrachloropropene to anisomerizer packed with clay granules, and isomerizing2,3,3,3-tetrachloropropene to 1,1,2,3-tetrachloropropene by heating thesecond dehydrochlorinator effluent in contact with said clay granules toa temperature of from about C. to about 200 C. for from about 0.4 toabout 2 hours and removing the isomerizer efiluent comprising theproduct 1,l,2,3- tetrachloropropene.

2. The process of Claim 1 wherein the chlorinations are carried out inthe presence of a free-radical forming catalyst.

3. The process of Claim 2 wherein said catalyst is a20-bisisobutyronitrile.

4. The process of Claim 1 wherein said feed stream is chlorinated sothat from about 30 to about 50 percent of the chlorinator efiluentremains as 1,2,3-trichloropropane.

5. The process of Claim 3 wherein 1,2,2,3-tetrachloropropane isrecovered from the fractionating column as a by-product.

6. The process of Claim 1 wherein the clay is attapulgite.

7. The process of Claim 1 wherein the second dehydrochlorinator effluentis isomerized under reflux conditions.

8. The process of Claim 7 wherein the second dehydrochlorinator efiluentis refluxed for from about 0.5 to about 1.3 hours.

v 8 References Cited UNITED STATES PATENTS 2,446,475 8/ 1948 Hearne etal 260-654 -R 3,398,204 8/1968 Gallant 260-654 R 2,420,975 5/1947 Plump260658 R 2,111,043 3/1938 Coss 260-654 D 2,485,507 10/1949 Perkins260654 D 3,028,439 4/1962 Thceling et a1. 260654 D US. Cl. X.R.

204163 R; 260-658 R, 654 D

